New Technique Can Stop Illegal Copying Of Your Photos, Videos

Scientists have developed an innovative light-based technique to create secure, invisible watermarks that can be used to prevent photos, videos and books from being illegally copied and distributed. In research, researchers use a complex pattern of light, or diffraction pattern, as a unique watermark. The invisible watermark is embedded into the content we are trying to protect. Imperceptibility is one of the most significant advantages of optical watermarking. The new approach encodes the optical watermark in a single step. It is faster, and uses a less complex optical setup than the optical watermarking approaches previously pursued, the researchers said. The technique can also be used to optically encrypt data or to hide information within images. The method is based on a technique called single-shot ptychography encoding (SPE) that uses multiple partially overlapping beams of light to generate a diffraction pattern from a complex object. Unlike other methods, SPE is also less prone to error than other methods. In addition to conducting numerical simulations to test their method, the researchers carried out an optical experiment showing the usefulness of SPE. Most methods for optical watermarking have only been demonstrated with simulations. This experiment shows that our method is suitable for practical optical watermarking. For the optical experiment, the researchers used SPE to create a watermark consisting of a diffraction pattern of multiple tiny spots. Prior to embedding the watermark into a host image, they used computer processing to remove any repeated data and to scramble the diffraction pattern, making it easier to embed the watermark and further improving its security. The spot size can be reduced to smaller than 10 microns, which helps prevent degradation of the host image. Once a watermark is embedded into digital media, there are multiple ways to detect it to check for authenticity. If someone knows an optical watermark is present, it can be detected by subtracting the host image and then using a special security key and extraction algorithm.